In a projectile, loom, the filling or weft yarns are drawn across the web of the cloth by a projectile shuttle, a flat metal cannister having a rounded nose. The shuttle travels across the web at high velocity and must be stopped in a very short distance at its end of travel on a terminal side of the loom. This stopping takes place as the shuttle passes into a gap between upper and lower brake pads, set to engage and stop the incoming projectile shuttle. The stopping position of the shuttle is indefinite, due to such variables as thickness, weight, and lubricity of each individual shuttle, and also due to wear on the brake pads. Accordingly, the brakes are intentionally set to stop the shuttle a short distance beyond the predetermined point at which the yarn is automatically released from the shuttle, and the shuttle thereafter is transferred to a conveyor chain for return to the opposite side of the loom. Shuttle returner apparatus is conventionally used for that purpose. When the shuttle enters the braking system, the shuttle returner is at rest a short distance beyond the region in which the shuttle is nominally stopped by the brakes. The nature and operation of shuttle returners in projectile looms is known to those skilled in the art.
In actual operation of a projectile loom, the incoming shuttles often overrun the braking system and strike the shuttle returner so that both the nose of the shuttle and the shuttle-receiving surface of the returner may become battered to the point that either or both components eventually must be replaced. This replacement of the shuttle returner is costly not only in the material and labor expense for replacement, but also in the down time incurred while the loom is withdrawn from operation to replace the broken or damaged parts.
Prior-art efforts to solve the foregoing problem generally have involved either making the shuttles or shuttle returners more durable in an effort better to withstand the repeated impacts, or refining the shuttle braking system so as to reduce shuttle overrun. A significant and more recent solution to the problem is found in U.S. Pat. No. 4,757,843, disclosing a shuttle returner having a relatively hard and inelastic shuttle receiving member attached to a relatively elastic body. The elastic body is connected to the reciprocating arm that cyclically advances and withdraws the shuttle returner on the loom. The impact force of an arriving shuttle striking the receiving member is mostly transferred into the elastic body member, which allows a brief deceleration period for the shuttle receiving member and the impacting shuttle. This deceleration and force absorption by the relatively elastic body member of the shuttle returner significantly reduces the relatively abrupt impact encountered with the shuttle returners of the prior art, and thereby reduces the physical damage to the shuttles and the shuttle receiving member.
Notwithstanding the improved results obtained through the shuttle returner apparatus disclosed in U.S. Pat. No. 4,757,843, on occasion the elastic body member of that shuttle returner has failed due to the tensile force repeatedly applied to the shuttle returner in operation. The operating arm of the loom repeatedly cycles the shuttle returner back and forth, first to push the shuttle back to the exact position for releasing the weft yarn, and then pulling the shuttle returner back into position to receive the next incoming shuttle beyond the brake pads. This push-pull movement is imparted to the shuttle returner at a high cyclical rate, due to the high operating speeds of projectile looms. Consequently, the shuttle returner parts and in particular the elastic body must withstand repeated compression and tension forces at relatively high rates of acceleration and deceleration. It has been found in practice that the elastic body members sometimes fail in response to the repeated abrupt application of tensile force tending to elongate or pull apart the elastic bodies.
Because the occasional failure of the elastic body members in the shuttle returner apparatus appear related to the relatively elastic nature of those bodies, making the bodies of a less-elastic material or of a composite plastic would appear a plausible solution to the problem. However, the elasticity of the shuttle returner body is important to the proper operation of the shuttle returner apparatus disclosed in the 4,757,843 patent, and reducing the elasticity to improve the longevity of the body members provides a commensurate and unwanted reduction in the overall effectiveness of the shuttle returner apparatus.